Bridge Tool for Producing Extruded Profiled Elements of Varying Cross-Section

ABSTRACT

The invention relates to a bridge tool for a device for directly extruding hollow profiled elements of variable wall thickness, comprising a die (6) and at least one mandrel element (5) having a first end facing the die opening and an opposite second end, the outer profile contour of a hollow profiled element being defined by the geometry of the die opening and the inner cross-section of a hollow profiled element being defined by the at least one mandrel element (5), characterized in that the at least one mandrel element (5) has at least one cut-out, in which an inner sliding mandrel is arranged, said inner sliding mandrel being mounted for movement in the axial direction, the inner sliding mandrel having different cross-sections in the first end region of the inner sliding mandrel facing the first end of the mandrel element.

RELATED APPLICATIONS

This application is a US National stage entry of International Application No. PCT/DE2018/100586, which designated the United States and was filed on Jun. 26, 2018, published in German, which claims priority to German Application No. 10 2017 114 371.8, filed Jun. 28, 2017.

The entire teachings of the above application(s) are incorporated herein by reference.

The present invention relates to a bridge-die tool for producing extruded profiles of varying cross section.

Extrusion is a forming process for producing different geometries, in particular rods or bars, tubes and profiles. In extrusion, a billet (block) which has been heated to forming temperature is pushed through a bridge die by a ram. The block here is enclosed by a container. The outer shape of the extruded section is determined here by the bridge die.

The prior art distinguishes between direct extrusion, indirect extrusion and hydrostatic extrusion.

In the case of direct extrusion, the ram pushes the block along the inner surface of the container in the direction of the bridge die. In the case of indirect extrusion, the container is closed at one end and the bridge die, which is located on the head of a hollow ram, is pressed onto the block from the other end. The extruded section passes through the bore in the ram. The diameter of said bore therefore delimits the circumscribing circle of the profile cross section. In the case of hydrostatic extrusion, the extruding force is applied to the block not directly by the ram, but via an active medium (water or oil).

The advantages of extrusion here, in general, are the low tool costs and the variety of geometries which can be produced.

Complex hollow profiles made of light metal can be produced by means of direct extrusion using porthole-die or bridge-die tools, wherein the bridge-die tools comprise a bridge-die part and a mandrel part. The outer contour here, as already explained, is determined by the bridge die and the inner shaping is determined by the mandrel.

The mandrel itself here, rather than being connected directly to the extrusion press, is connected to the mandrel part of the tool via carrying arms or bridges. The block itself, first of all, is split into sub-sections by the entry chambers made in the mandrel part and, thereafter, is brought back together again, at high pressure and temperature, in the welding chamber of the bridge die.

The bridge-die tools here are subjected to extreme mechanical and thermal stressing, which is problematic in particular on the mandrel-carrying arms. It is also possible for fracturing to occur as a result of notch stressing at the roots of the mandrel.

The disadvantage with the extrusion processes which are known from the prior art is that only profiles of a constant cross section can be produced. As a result, the profiles are over-dimensioned at many locations, since the profiles always have to be designed over their entire length in accordance with the requirements which have to be met at the location of highest loading.

In order to produce varying cross sections in an extrusion press, DE 10 02 18 81 A1 teaches an extrusion apparatus in which a mandrel is designed such that it can be altered in the axial extruding direction and which has different cross sections in its end region.

Depending on the arrangement of the end regions of the mandrel described in said document relative to the bridge die, an annular gap of different diameter is formed for the purpose of forming different profile cross sections.

However, the disadvantage with a solution according to DE 10 02 18 81 A2 is that, although the document discloses an apparatus comprising a porthole-die tool, said apparatus being intended to provide for a varying cross section of the extrusion profile, the mandrel as a whole, which for technical reasons is long, has to be moved axially. The resulting long lever arms give rise to the mandrel oscillating to a relatively great extent. Such oscillation, however, prevents profiles being produced with a high level of precision and narrow tolerances.

It is also disadvantageous that the durability of a mandrel according to DE 10 02 18 81 A1 is reduced. During use, such a mandrel is subjected to high thermomechanical stressing, which depends in particular on the extruding forces which occur and on the forming temperatures. In particular the long mandrel-carrying arm is exposed to alternating tensile and bending forces, which can be accompanied by local thermal stressing.

The object of the present invention, then, is to overcome the disadvantages of the prior art and, in particular, to provide an apparatus in order to produce profiles of a variable cross section with a high level of precision, since it is only such a high level of precision which can effectively avoid over-dimensioning of the profiles, wherein the apparatus is, as it were, designed, and intended, to withstand the thermomechanical stressing to an optimum extent.

This object is achieved according to the invention by a bridge-die tool for an apparatus for the direct extrusion of hollow profiles of variable wall thickness, comprising a bridge die and at least one mandrel element having a first end, which is directed toward the bridge-die opening, and a second end, which is located opposite the first end, wherein the outer contour of a hollow profile is defined by the geometry of the bridge-die opening and the inner cross section of a hollow profile is defined by at least one mandrel element, wherein the at least one mandrel element has at least one cutout, in which an inner displacement mandrel is mounted in an axially movable manner, wherein the inner displacement mandrel has different cross sections in its first end region, which is directed toward the first end of the mandrel element.

The invention here is based on the surprising finding that it is possible to produce hollow profiles of varying internal diameter when the mandrel is constructed in a number of parts, wherein a movable inner displacement mandrel with different cross sections at its end regions is included, and the axial movement of said displacement mandrel results in the inner cross section of the hollow profile being altered.

It can be advantageous here, in particular, for the inner displacement mandrel to have the smallest cross section at its first end, and therefore an axial displacement of the inner displacement mandrel in the direction of the bridge die, or into the bridge die, results in a smaller wall thickness of the hollow profile, since the shaping gap between the inner displacement mandrel and bridge die decreases.

The disadvantages of the prior art are overcome here as a result of the mandrel being in at least two parts. The inner displacement mandrel can be brought into operative connection with drive elements by means of connecting elements, via short lever arms, in order for said displacement mandrel to be displaced axially, oscillation of the mandrel therefore being minimized. Provision can also be made for oscillation of the inner displacement mandrel to be more or less prevented altogether as a result of specific guide elements.

The inner displacement mandrel according to the invention therefore provides for hollow profiles of varying cross section to be produced with a high level of precision.

Movements of the inner displacement mandrel and of further elements of the bridge-die tool according to the invention are given here relative to the extruding direction. An axial displacement here basically describes a displacement in the extruding direction, or parallel to the extruding direction, and a radial displacement describes a radial displacement relative to the extruding direction.

It can be advantageous according to the invention for the mandrel element to comprise at least one second axial cutout, which extends axially along the second end region of the inner displacement mandrel, said second end region being located opposite the first end region of the inner displacement mandrel, wherein a transverse slide which is arranged, in particular more or less, perpendicularly to the at least one mandrel element is included and is introduced, at least in part, into the at least one second cutout, and wherein the transverse slide is in operative connection with the inner displacement mandrel, in particular is fixed to the inner displacement mandrel.

A transverse slide according to the invention can be used for transmitting force from a drive device to the inner displacement mandrel, wherein the drive device can be arranged preferably outside the actual bridge-die tool, for example on the outer wall of the container or of the holder of the bridge-die tool.

It can be advantageous here, in particular, if the transverse slide can be brought into operative connection, or is in operative connection, with at least one drive device directly or by means of at least one crossmember, wherein the drive device is designed, and intended, to move the transverse slide and the inner displacement mandrel in the axial direction.

It can likewise be advantageous here if, rather than force transmission from the drive device to the inner displacement mandrel taking place just with the interposition of the transverse slide, a crossmember is arranged, in addition, between the drive device and the transverse slide.

It can also be preferred here if a first crossmember is arranged at a first radial end of the transverse slide and a second crossmember is arranged at a second radial end of the transverse slide, said second radial end being located opposite the first radial end, wherein the first crossmember can be brought into operative connection, or is in operative connection, with a first drive device and/or the second crossmember can be brought into operative connection, or is in operative connection, with a second drive device.

Using two crossmembers arranged at opposite ends of the transverse slide can result in uniform, parallel force transmission from the drive devices to the inner displacement mandrel and, at the same time, prevent skewing of the latter. As an alternative, provision can also be made so that, instead of a second drive device being present, the two crossmembers can be connected, or are connected, to a single drive device.

It has proven advantageous here for the first and/or the second drive device to be designed in the form of a linear drive, in particular in the form of a hydraulic cylinder.

It has been found that in particular hydraulic cylinders have proven particularly suitable for producing a linear force, in order to provide for an axial displacement of the inner displacement mandrel.

It can also be advantageous, according to one embodiment of the invention, for the inner displacement mandrel to have a trapezoidal or triangular cross section, in part, in the region of its first end, as seen in the axial direction.

The present invention is not restricted here to the trapezoidal or triangular cross sections given by way of example. Rather, the cross section is determined in dependence on the number of movable displacement elements.

Provision can be made here, according to one embodiment, for the interior angle or angle of gradient β of the trapezoidal or triangular cross section a value ranging from 5 to 25°, preferably from 8 to 15°, particularly preferably of 10°. It is possible here for the optimum angle to be adapted/selected according to the invention, even outside the preferred ranges, in accordance with the drive and/or the amount of installation space available for minimizing the amount of force required (small angle, long displacement distance) or for minimizing the amount of installation space (large angle, short displacement distance).

Provision can likewise advantageously be made here for the inner displacement mandrel to be in operative connection with at least one wedge-shaped element on or in the region of its first end, or for said wedge-shaped element to be brought into abutment, in part, with the inner displacement mandrel, wherein in particular the further angle of gradient β of that side of the at least one wedge-shaped element which is directed toward the inner displacement mandrel is smaller than, or equal to, the angle of gradient β, and therefore an axial displacement of the inner displacement mandrel is converted into a corresponding radial displacement of the at least one wedge-shaped element.

According to the invention, in addition to the radially movable inner displacement mandrel, use can be made, for the purpose of altering the inner cross section of a hollow profile, of at least one wedge-shaped element, of which the radial displacement relative to the inner displacement mandrel directly influences the wall thickness of the hollow profile.

It has proven advantageous here, according to the invention, for a radial movement of the inner displacement mandrel in the direction of, or further into, the bridge die to result in a spreading movement of the at least one wedge-shaped element in the radial direction, since the smallest cross section of the inner displacement mandrel is arranged at the first end of the latter.

This has, in particular, the advantage that, rather than having to be absorbed exclusively by the inner displacement mandrel, the high forces which occur are also absorbed by the at least one wedge-shaped element.

Furthermore, more or less free design capability in respect of the at least one wedge-shaped element, also irrespective of the geometry of the inner displacement mandrel, allows the inner cross section and the wall thickness of the hollow profile to be varied.

According to the invention, the wedge-shaped element can have different base surfaces and the acute angle of the wedge can be formed from two or more sides.

It has proven advantageous for at least one second wedge-shaped element to be arranged in mirror-symmetrical fashion in relation to the first wedge-shaped element on that side of the inner displacement mandrel which is located opposite the first wedge-shaped element.

Using two wedge-shaped elements arranged in mirror-symmetrical fashion here provides for simultaneous alteration of the wall thickness on two sides of a hollow profile. It is clear here that it is also possible to use more than two wedge-shaped elements, which can be grouped radially around the inner displacement mandrel.

It has also been found that the at least one wedge-shaped element is advantageously connected to the mandrel element by means of a first dovetail guide, wherein the at least one first dovetail guide provides for movement of the at least one wedge-shaped element exclusively in the radial direction, wherein the dovetail guide is formed in particular by the mandrel element and the at least one wedge-shaped element.

A first dovetail guide according to the invention provides for the at least one wedge-shaped element to be movable exclusively in the radial direction, but not in the axial direction. This results in particular, in the situation where an axial movement of the inner displacement mandrel with its axially varying cross section results exclusively in a radial movement of the at least one wedge-shaped element. Furthermore, skewing of the wedge-shaped element is prevented and it is ensured that the action of the axial movement of the inner displacement mandrel being converted into the radial movement of the at least one wedge-shaped element can be reproduced.

According to one embodiment of the present invention, it has proven particularly advantageous, in addition, for the inner displacement mandrel and the at least one wedge-shaped element to be connected by means of an axially formed second dovetail guide, and therefore an axial movement of the inner displacement mandrel is converted into a radial movement of the at least one wedge-shaped element.

The second dovetail guide according to the invention provides, in particular, the advantage that there is a reliable connection between the inner displacement mandrel and the at least one wedge-shaped element. Furthermore, the second dovetail guide is particularly advantageous since it ensures not only that, upon movement of the inner displacement mandrel in the direction of, or into, the bridge die, the at least one wedge-shaped element moves radially outward, but also that, upon movement of the inner displacement mandrel in the opposite direction, tensile forces act on the at least one wedge-shaped element in order to reduce the radial spreading action of the wedge-shaped element.

Furthermore, provision can be made for the first cutout of the mandrel element and the at least one inner displacement mandrel to form a third dovetail guide in the axial direction, and therefore the inner displacement mandrel and the mandrel element are connected to one another by means of a dovetail guide.

This has, in particular, the advantage that skewing of the inner displacement mandrel is prevented, even when high forces are involved.

The invention also provides a direct-extrusion apparatus comprising a bridge-die tool according to the invention.

Finally, the invention provides for the use of a bridge-die tool according to the invention so that one or more extruded profiles of cross sections which vary in the extruding direction are produced in a direct-extrusion apparatus. The invention is therefore based on the surprising finding that it is possible to alter the profile wall thicknesses during the extrusion process, while avoiding the disadvantages of the prior art, in that an inner displacement mandrel can be displaced axially by means of a transverse slide, which in turn is connected to linear drives by means of two oppositely located crossmembers. If the transverse slide is moved axially, it is therefore the case that, as it were, the inner displacement mandrel is displaced in the axial extruding direction. The wedge-shaped elements here, which are optionally in operative connection with the inner displacement mandrel, deflect said axial movement, preferably by means of a second dovetail guide, into a radial movement, which is arranged perpendicularly to the axial movement. This results in the wedge-shaped element or elements spreading apart and, on the basis of this wedge movement, the shaping gap between the wedge-shaped element and bridge die is reduced and, consequently, the wall thickness of the hollow profile is reduced.

In order for the wall thickness to be subsequently increased, the linear drives are displaced into the starting position again, that is to say counter to the extruding direction. This movement also pulls back the crossmembers, including the transverse slide. As a result of this return movement of the inner displacement mandrel, said displacement is transmitted, via the optional second dovetail guide, to the wedge-shaped element or elements, and therefore these move radially in the direction of the inner displacement mandrel. The shaping gap is increased again as a result.

Further features and advantages of the invention can be gathered from the following description, in which exemplary embodiments of the invention will be explained by way of example with reference to schematic drawings, without restricting the invention as a result.

In the drawings:

FIG. 1: shows a perspective view of one embodiment of a bridge-die tool according to the invention;

FIG. 2: shows a schematic view of the bridge-die tool according FIG. 1;

FIG. 3: shows a schematic side view, in section, of the bridge-die tool according to FIG. 1; and

FIG. 4: shows a perspective view of one embodiment of a mandrel element of a bridge-die tool according to the invention.

FIG. 1 illustrates a perspective view of one embodiment of a bridge-die tool according to the invention. The latter comprises a container 1, on the outer sides of which are arranged two linear drives 2 in the form of hydraulic cylinders. Each of the linear drives 2 here is connected to a crossmember 3, the crossmembers terminating on two opposite sides of a transverse slide 4 and being connected to the latter in a form-fitting manner. The gap between a mandrel element 5 and the bridge die 6 here defines the wall thickness of the hollow profiles which are to be produced. The bridge die 6 here is fastened on a pressure-exerting plate 7. The mandrel element 5 here additionally comprises wedge-shaped elements 8 and also an inner displacement mandrel 9.

FIG. 2 illustrates a plan view, in section, of the bridge-die tool according to FIG. 1. In common with the side view, in section, in FIG. 3, the functional principle of a bridge-die tool according to the invention is clearly evident. The inner displacement mandrel 9 here is arranged in a first cutout 10, which extends in the axial direction and is adjoined by two second cutouts 11 for the transverse slide 4. Movement of the linear drives 2 results in displacement of the crossmembers 3 and of the transverse slide 4, and therefore of the inner displacement mandrel 9, in the radial direction. This axial displacement of the inner displacement mandrel 9 here results in a radial movement of the wedge-shaped elements 9, and therefore in alteration of the gap between the mandrel element 5 and the bridge die 6. This alteration in the gap results in the cross section of the hollow profile which is to be produced altering.

FIG. 4 shows, in addition, two first dovetail guide 13 for the wedge-shaped elements 8 and also two second dovetail guides 14. Said first dovetail guides 13 ensure that the wedge-shaped elements 8 can move exclusively in the radial direction, whereas the second dovetail guides 14 mean that, alongside radially outwardly acting compressive forces, during displacement of the inner displacement mandrel 9, also tensile forces can be transmitted from the inner displacement mandrel 9 also the wedge-shaped elements 8.

The features of the invention which are disclosed in the foregoing description, the claims and the drawings can be essential both individually, and in any desired combination, for implementing the invention in its various embodiments. 

1. A bridge-die tool for an apparatus for the direct extrusion of hollow profiles of variable wall thickness, comprising a bridge die and at least one mandrel element having a first end, which is directed toward the bridge-die opening, and a second end, which is located opposite the first end, wherein the outer contour of a hollow profile is defined by the geometry of the bridge-die opening and the inner cross section of a hollow profile is defined by at least one mandrel element, characterized in that the at least one mandrel element has at least one cutout, in which an inner displacement mandrel is mounted in an axially movable manner, wherein the inner displacement mandrel has different cross sections in its first end region, which is directed toward the first end of the mandrel element.
 2. The bridge-die tool as claimed in claim 1, characterized in that the mandrel element comprises at least one second axial cutout, which extends axially along the second end region of the inner displacement mandrel, said second end region being located opposite the first end region of the inner displacement mandrel, wherein a transverse slide which is arranged, in particular more or less, perpendicularly to the at least one mandrel element is included and is introduced, at least in part, into the at least one second cutout, and wherein the transverse slide is in operative connection with the inner displacement mandrel, in particular is fixed to the inner displacement mandrel.
 3. The bridge-die tool as claimed in claim 2, characterized in that the transverse slide can be brought into, or is in, operative connection with at least one drive device directly or by means of at least one crossmember, wherein the drive device is designed, and intended, to move the transverse slide and the inner displacement mandrel in the axial direction.
 4. The bridge-die tool as claimed in claim 3, characterized in that a first crossmember is arranged at a first radial end of the transverse slide and a second crossmember is arranged at a second radial end of the transverse slide, said second radial end being located opposite the first radial end, wherein the first crossmember can be brought into, or is in, operative connection with a first drive device and/or the second crossmember can be brought into, or is in, operative connection with a second drive device.
 5. The bridge-die tool as claimed in one of claims 2 to 4, characterized in that the first and/or the second drive device are/is designed in the form of a linear drive, in particular in the form of a hydraulic cylinder.
 6. The bridge-die tool as claimed in one of the preceding claims, characterized in that the inner displacement mandrel has a trapezoidal or triangular cross section, in part, in the region of its first end, as seen in the axial direction.
 7. The bridge-die tool as claimed in claim 6, characterized in that the inner displacement mandrel is in operative connection with at least one wedge-shaped element on or in the region of its first end, or said wedge-shaped element is brought into abutment, in part, with the inner displacement mandrel, wherein in particular the further angle of gradient β of that side of the at least one wedge-shaped element which is directed toward the inner displacement mandrel is smaller than, or equal to, the angle of gradient β, and therefore an axial displacement of the inner displacement mandrel is converted into a corresponding radial displacement of the at least one wedge-shaped element.
 8. The bridge-die tool as claimed in claim 7, characterized in that at least one second wedge-shaped element is arranged in mirror-symmetrical fashion in relation to the first wedge-shaped element on that side of the inner displacement mandrel which is located opposite the first wedge-shaped element.
 9. The bridge-die tool as claimed in claim 7 or claim 8, characterized in that the at least one wedge-shaped element is connected to the mandrel element by means of a first dovetail guide, wherein the at least one dovetail guide provides for movement of the at least one wedge-shaped element exclusively in the radial direction, and wherein the dovetail guide is formed in particular by the mandrel element and the at least one wedge-shaped element.
 10. The bridge-die tool as claimed in one of claims 7 to 9, characterized in that the inner displacement mandrel and the at least one wedge-shaped element are connected by means of an axially formed second dovetail guide, and therefore an axial movement of the inner displacement mandrel is converted into a radial movement of the at least one wedge-shaped element.
 11. The bridge-die tool as claimed in one of the preceding claims, characterized in that the first cutout of the mandrel element and the at least one inner displacement mandrel form a third dovetail guide in the axial direction, and therefore the inner displacement mandrel and the mandrel element are connected to one another by means of a dovetail guide.
 12. A direct-extrusion apparatus comprising a bridge-die tool as claimed in one of the preceding claims.
 13. The use of a bridge-die tool as claimed in one of claims 1 to 11 so that one or more extruded profiles of cross sections which vary in the extruding direction are produced in a direct-extrusion apparatus. 